This invention relates to a prosthetic medical device and methods, and more particularly to implantable eyelid devices and methods for controlling the opening and closing of an eyelid.
Injury or neurological disorders, such as Bell""s palsy, myasthenia gravis, and Lou Gehrig""s disease (amyotrophic lateral sclerosis), cause one or both of the upper and/or the lower eyelids to droop and to stop their natural blinking. When this occurs the eye surface dries out, leading to pain and discomfort, infection, blindness, and possibly loss of the eye.
Traditional treatments for this condition include implanted eyelid weights or springs, lubricating eye drops, and surgical suturing or taping of the eyelids shut. Various disadvantages exist for each of these existing treatments, e.g., the use of implanted eyelid weights may cause the eyelid to open when opening is not desired.
The structure of the eyelid 56 is shown in FIG. 1. The muscle fibers of the orbicularis oculi 50 surround the palpebral fissure, which is the slit between the upper and lower lids. The function of the orbicularis oculi 50 is to close the eye. The palpebral part 52 sweeps in curves in the upper and lower eyelids. On contraction, the eyelids are closed gently. The orbital part 54 sweeps in concentric curves in the forehead and cheek as a flat, thin sheet of muscle. Contraction lowers the eyebrow, and when this muscle contracts with the palpebral part 52, the eyes are squeezed tightly shut. The orbicularis oculi 50 can fail to contract in a damaged, partially denervated eyelid, thus there is a loss of eyelid blinking.
The levator palpebrae superioris 58 functions to elevate the upper eyelid, thus opposing the orbicularis oculi 50 muscle. The frontalis-occipitalis 60 elevates the eyebrows and is a dilator of the palpebral fissure.
Depending on the cause of the inability to close or open an eyelid, one possible solution is to stimulate the muscle or nerve of the nonfunctioning eyelid. A number of approaches have been proposed, such as in U.S. Pat. Nos. 4,799,487 and 5,843,147. U.S. Pat. No. 5,843,147 presents an implantable electrode approach to solving this problem. For any such stimulus system to be efficiently utilized, the electrode for the system must be designed such that it can be easily implanted, is chronically stable once implanted, and provides electrical stimulation without causing pain to the patients. For example, it is important to avoid stimulation of surrounding facial muscles or nearby sensory nerves. Current known electrodes do not provide all of such functionality as applicable to the eyelid, eye, and surrounding area.
It is well known that electrical stimulation of the retina may have a beneficial effect on certain degenerative eye diseases. For example, U.S. Pat. No. 6,275,735 describes normal retinal cell function as a photochemical reaction converting light energy to an electrical impulse that travels to the brain and vision occurs. With age-related macular degeneration (AMD) and other visual system diseases, diseased, inflamed retinal cells eventually lose cell function. Adenosine triphosphate (ATP) levels drop, protein synthesis drops, the electrical resistance goes up, and cell membrane electrical potential goes down. The cells may go dormant for a time before they die. If electrical stimulation is provided to the cells before they die, blood vessel permeability is increased, a more normal cellular electrical potential will be achieved, the ATP levels will increase, protein synthesis will occur again, and normal cell metabolism will be restored. In addition, electrical stimulation appears to have a healing effect on the small blood vessels in the retina, promoting a more efficient delivery of nutrients to the retinal cells and a more efficient uptake of proteins that can accumulate on the retina. Thus, microcurrent stimulation will help rejuvenate the cells in the retina to slow or stop degeneration of the eye due to AMD. With the proper microcurrent stimulation waveform and therapy procedures, AMD may be slowed or stopped in a large number of people suffering from the disease.
For the reasons indicated above and for other reasons which will become apparent from the detail below, improved implantable eyelid electrode devices and methods of implanting such devices are needed. It is therefore the object of the present invention to provide such electrodes and to provide methods for closing or opening an eyelid by closed or open loop methods.
The apparatus of the instant invention is an implantable miniature stimulator and/or sensor for eyelids. The device is surgically implanted on or near a nerve or muscle that controls the blinking function of an eyelid. Electrical pulses are transmitted from a control device that may be located remotely from the stimulator, and which may be implanted in the body. The stimulating electric pulses travel along an electrically insulated cable that contains a number of very small diameter wires. The wires pass through an electrically insulating silicone body and down a leaflet body where they are attached to an electrode. The electrode rests on the nerve or muscle to be stimulated.
In an open loop control case, an electrical stimulating pulse is transmitted to the electrodes, at intervals on the order of several times per minute, which causes the paralyzed eyelid to open or close for normal blinking. Alternatively, the feedback signal in a closed loop control case may be generated in response to a sensor on a functional eyelid, responsive to a neurostimulator muscular signal, which is then used to trigger stimulation of the paralyzed eyelid. In both cases, the input stimulation signal may be adjusted to give a satisfactory and consistent response.
It is an object of the invention to provide an implantable miniature array suitable to cause an eyelid to blink.
It is an object of the invention to provide an implantable miniature array.
It is an object of the invention to provide a biocompatible miniature implant that is connected by an electrical connection to a remote control device.
It is an object of the invention to provide a method of controlling the opening and closing of a non-functioning eyelid with a signal from the functioning eyelid.
It is an object of the invention to provide a closed loop method of controlling the stimulating array signal.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.